In general, ink jet printing machines or printers include at least one printhead that ejects drops or jets of liquid ink onto a recording or image forming media. A phase change ink jet printer employs phase change inks that are in the solid phase at ambient temperature, e.g. around 25° C., but transition to a liquid phase at an elevated temperature. The molten ink can then be ejected onto a printing media by a printhead directly onto an image receiving substrate, or indirectly onto an intermediate imaging member before the image is transferred to an image receiving substrate. Once the ejected ink is on the image receiving substrate, the ink droplets quickly solidify to form an image.
Once melted phase change ink has been deposited on a recording medium, the recording medium may be transferred, delivered, or otherwise moved to a finishing device, or finisher. A “finisher” can be any post-printing accessory device such as a tray or trays, sorter, mailbox, inserter, interposer, stapler, stacker, hole puncher, collator, stitcher, binder, envelope stuffer, postage machine, or the like. In addition, the finisher may include a folding apparatus. The folder apparatus can be any combination of hardware elements that enables the print media to be folded. Mechanical folding of sheets involves doubling the sheet between rollers while applying pressure appropriate to the thickness of the paper to create a sharp fold that substantially eliminates the paper's natural tendency to revert to its original shape. In various exemplary embodiments, the folding apparatus can include any hardware elements, such as fold blades, one or more simple buckle folders, one or more sets of drive rollers, etc, that enable various types of folds to be controllably applied to each sheet on a sheet-to-sheet basis. The type of folds performed by the folder apparatus may include, but is not limited to, c-folds, z-folds, and half-folds.
One difficulty faced in folding print media that have been printed with phase change ink, however, is the breaking or flaking off of ink from the print media. For example, folding operations in a finishing system are typically performed at a rather high rate of speed which may cause solid ink to break and subsequently flake off because the solid ink material cannot respond quickly enough to the folding operation. In addition, ink breaking or flaking due to folding may result because phase change ink tends to be deposited primarily on the surface of the print media. Therefore, folding the print media may cause solidified phase change ink that has solidified on the surface of the media to break or flake off the media.